A process of manufacturing a semiconductor device in which a stacking structure of an integrated circuit is formed on the surface of a substrate to be processed, such as a semiconductor wafer (hereinafter, referred to as a wafer) includes a liquid processing process of processing the wafer surface by using a liquid to remove minute dusts or a native oxide layer on the wafer surface with a washing fluid such as a chemical solution.
For example, a single-type spin washing apparatus washing the wafer removes dusts or a native oxide on the wafer surface by rotating the wafer while supplying, for example, alkaline or acid chemical solutions to the surface of the wafer by using a nozzle. In this case, after remaining chemical solutions are removed by rinse washing using, for example, deionized water from the wafer surface, the wafer surface is dried by a spin dry where remaining solutions are brushed away while rotating the wafer.
However, with high integration of the semiconductor device, a problem such as so-called a pattern collapse has grown serious in a processing of removing the solutions. The pattern collapse is a phenomenon in which the balance of a surface tension horizontally pulling the convex portion is lost, and, as a result, the convex portions fall down toward the side where more solutions remain at the time of drying the remaining solutions on the wafer surface, as solutions remaining at the left and right sides of a convex portion of concave and convex portions forming a pattern are unevenly dried.
As a technique of removing the solutions remaining on the water surface while suppressing the pattern collapse, a drying method using a supercritical state fluid (a supercritical fluid) is widely known. The viscosity of the supercritical fluid is lower than a liquid and the ability to dissolve is higher than the liquid. In addition, there is no interface between the supercritical fluid and the liquid or gas which is in equilibrium state with the supercritical fluid. Therefore, the wafer attached with the liquid is substituted with the supercritical fluid, and thereafter, when the supercritical fluid is changed to a gaseous state, the liquid may be dried without being influenced by the surface tension.
Herein, Japanese Patent Application Laid-Open No. 2008-72118 discloses a technology in which a substrate washed by a washing unit is transferred into a drying apparatus by a substrate transferring robot and the substrate makes contacts to the supercritical fluid in the drying apparatus to remove a washing fluid attached to the surface of the substrate. In the technology disclosed in Japanese Patent Application No. 2008-72118, a substrate to be processed is carried into a transfer chamber and transferred to the transferring robot. The substrate is then transferred to a drying processing chamber and the corresponding substrate is dried by using the supercritical fluid. As a result, the surface of the substrate remains to be exposed to a gaseous atmosphere until the processing starts. Therefore, since the liquid on the surface of the substrate is dried until the processing by the supercritical fluid starts, a pattern may be collapsed. Further, since the transferring robot keeps the substrate in a horizontal direction, dusts such as particles attached to the substrate are wound up by the supercritical fluid, and, thereafter, dropped to the surface of the substrate, which may contaminate a forming area of the semiconductor device. See, for example, Japanese Patent Application No. 2008-72118: Paragraphs [0025] to [0029] and FIG. 1.